Switched common-mode current control for single-inductor-multiple-output (SIMO) power converters

ABSTRACT

A power converter includes a voltage source for generating an input voltage, and a regulation circuit for generating a set of output voltages based on the input voltage. The regulation circuit regulates the set of output voltages in different manners based on whether the set of output voltages is greater or less than a set of corresponding reference voltages, respectively. If one or more output voltages are less than one or more of the corresponding reference voltages, the regulation circuit regulates only those one or more output voltages during a current regulation interval based on an error voltage related to one or more differences between the one or more output voltages and the corresponding one or more reference voltages, respectively. If all output voltages are greater than the corresponding reference voltages, the regulation circuit regulates only the output voltage associated with the largest load current during the current regulation interval.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the filing date of U.S.Provisional Application, Ser. No. 62/725,037, filed on Aug. 30, 2018,which is incorporated herein by reference.

FIELD

Aspects of the present disclosure relate generally to power converters,and in particular, to a switched common-mode current control forsingle-inductor-multiple-output (SIMO) power converters.

DESCRIPTION OF RELATED ART

In certain applications, there is a need for regulating a set of outputvoltages applied across a set of loads, respectively. For circuit spaceefficiency and/or other reasons, power converters have been designedusing a single inductor for regulating a set of output voltages. In suchpower converters, there is a desire to regulate the set of outputvoltages in an accurate and power efficient manner.

SUMMARY

The following presents a simplified summary of one or more embodimentsin order to provide a basic understanding of such embodiments. Thissummary is not an extensive overview of all contemplated embodiments,and is intended to neither identify key or critical elements of allembodiments nor delineate the scope of any or all embodiments. Its solepurpose is to present some concepts of one or more embodiments in asimplified form as a prelude to the more detailed description that ispresented later.

An aspect of the disclosure relates to an apparatus including a voltagesource configured to generate an input voltage; and a regulation circuitconfigured to generate a set of output voltages based on the inputvoltage, wherein the regulation circuit is configured to regulate theset of output voltages in different manners based on whether the set ofoutput voltages are greater or less than a set of correspondingreference voltages, respectively.

Another aspect of the disclosure relates to a method includinggenerating an input voltage; generating a set of output voltages basedon the input voltage; and regulating the set of output voltages indifferent manners based on whether the set of output voltages aregreater or less than a set of corresponding reference voltages,respectively.

Another aspect of the disclosure relates to an apparatus including meansfor generating an input voltage; means for generating a set of outputvoltages based on the input voltage; and means for regulating the set ofoutput voltages in different manners based on whether the set of outputvoltages are greater or less than a set of corresponding referencevoltages, respectively.

To the accomplishment of the foregoing and related ends, the one or moreembodiments include the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative aspects ofthe one or more embodiments. These aspects are indicative, however, ofbut a few of the various ways in which the principles of variousembodiments may be employed and the description embodiments are intendedto include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a schematic diagram of an exemplary prior artswitched-mode, single-inductor-single-output (SISO) power converter.

FIG. 1B illustrates a timing diagram of exemplary states of switches andinductor current associated with an operation of the prior art powerconverter of FIG. 1A.

FIG. 2A illustrates a schematic diagram of an exemplary prior artcommon-mode current control, single-inductor-multiple-output (SIMO)power converter.

FIG. 2B illustrates a timing diagram of exemplary states of switches andinductor current associated with an operation of the prior art powerconverter of FIG. 2A.

FIG. 3A illustrates a schematic diagram of another exemplary prior artcurrent control, single-inductor-multiple-output (SIMO) power converter.

FIG. 3B illustrates a timing diagram of exemplary states of switches andinductor current associated with an operation of the prior art powerconverter of FIG. 3A.

FIG. 4A illustrates a schematic diagram of another exemplary switchedcommon-mode current control, single-inductor-multiple-output (SIMO)power converter in accordance with another aspect of the disclosure.

FIG. 4B illustrates a table of states of various signals and switchesassociated with an operation of the power converter of FIG. 4A inaccordance with another aspect of the disclosure.

FIG. 5 illustrates a schematic diagram of an exemplary regulationcircuit for controlling a timing of the closure of switches of a powerconverter in accordance with another aspect of the disclosure.

FIG. 6 illustrates a schematic diagram of another exemplary switchedcommon-mode current control, single-inductor-multiple-output (SIMO)power converter in accordance with another aspect of the disclosure.

FIG. 7 illustrates a flow diagram of an exemplary method of operatingthe power converter of FIG. 6 in accordance with another aspect of thedisclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with theappended drawings, is intended as a description of variousconfigurations and is not intended to represent the only configurationsin which the concepts described herein may be practiced. The detaileddescription includes specific details for the purpose of providing athorough understanding of the various concepts. However, it will beapparent to those skilled in the art that these concepts may bepracticed without these specific details. In some instances, well-knownstructures and components are shown in block diagram form in order toavoid obscuring such concepts.

FIG. 1A illustrates a schematic diagram of an exemplary prior artswitched-mode, single-inductor-single-output (SISO) power converter 100.The power converter 100 includes a voltage source 110 and a regulationcircuit including an inductor L, a switching network 115 includingswitches S0 and S1, an error amplifier 120, and a duty cycle controller130. The regulation circuit processes an input voltage Vin generated bythe voltage source 110 to generate and regulate an output voltage Voutfor a load 190.

The voltage source 110, which may be configured as a battery or othertype of voltage source, generates the input voltage Vin at its positiveterminal, and includes a negative terminal coupled to ground. Theinductor L is coupled between the positive terminal of the voltagesource 110 and a first terminal of switch S1. The switch S1 includes asecond terminal coupled to an output of the power converter 100 (thenode at which the output voltage Vout is generated). The load 190 iscoupled between the output of the power converter 100 and ground. Theswitch S0 is also coupled between the first terminal of switch S1 outputof the power converter 100 and ground.

The error amplifier 120 includes a first input configured to receive theoutput voltage Vout, and a second input configured to receive areference voltage Vref. The reference voltage Vref is the target voltagefor the output voltage Vout. The error amplifier 120 generates an errorvoltage Verr related to a difference between the output voltage Vout andthe reference voltage Vref. The duty cycle controller 130, whichreceives a substantially periodic clock CLK, generates a control signalduty_siso for controlling the duty cycle ΔT_(S0)/T_(CLK) associated withthe switches S0 and S1 turned on and off based on the error voltageVerr, respectively.

FIG. 1B illustrates a timing diagram of exemplary states of the switchesS0 and S1 and the current I_(L) flowing through the inductor Lassociated with the operation of the prior art power converter 100. Attime t0 or the beginning of a regulation clock period T_(CLK), the dutycycle controller 130 generates the control signal duty_siso to turn onthe switch S0 and turn off switch S1. While the switches S0 and S1 arerespectfully turned on and off, a current I_(L) flowing through theinductor L increases with a slope related to Vin/L, where L is theinductance of the inductor L. The rising inductor current I_(L) causesthe inductor L to store energy in the form of a magnetic field.

At time t1, the duty cycle controller 130 generates the control signalduty_siso to turn off the switch S0 and turn on switch S1. The dutycycle ΔT_(S0)/T_(CLK) or duration of the time interval t0-t1 is relatedto the error voltage Verr. For example, if the error voltage Verr issmall, the duty cycle ΔT_(S0)/T_(CLK) is small so as not to generate alot of magnetic energy stored in the inductor L. Conversely, if theerror voltage Verr is large, the duty cycle ΔT_(S0)/T_(CLK) is large togenerate a lot of magnetic energy stored in the inductor L.

During time interval t1-t2 or the remaining time interval of the clockperiod T_(CLK), the duty cycle controller 130 generates the controlsignal duty_siso to maintain switch S0 turned off and switch S1 turnedon. The stored magnetic energy created in the inductor L during timeinterval t1-t2 produces an inductor current I_(L) that decreases with aslope related to (Vout−Vin)/L. As switch S1 is turned on, the currentI_(L) flows to the output so as to change the output voltage Vout by anamount related to the error voltage Verr. This results in the outputvoltage Vout being regulated to be substantially equal to the referencevoltage Vref. The above cycle is repeated to maintain the output voltageVout substantially equal to the reference voltage Vref.

Because, in power converter 100, there is a single inductor and a singleoutput, the regulation of the output voltage Vout as discussed is prettystraight forward and operates well. However, there are power convertersthat include a single inductor but has multiple outputs (referred toherein as single-inductor-multiple-output (SIMO) power converters),where the regulation of multiple output voltages presents complexity andcompromises to a designer. For example, some SIMO power convertersregulate the multiple output voltages with the acceptance of common-modeerrors in the output voltages. Other SIMO power converters regulate themultiple output voltages with substantially no common-mode error in theoutput voltages, but with a reduction in power conversion efficiency. Acouple of exemplary power converters with the above attributes arediscussed below, respectively.

FIG. 2A illustrates a schematic diagram of an exemplary prior artcommon-mode current control, single-inductor-multiple-output (SIMO)power converter 200. The power converter 200 includes a voltage source210 and a regulation circuit including an inductor L, a switchingnetwork 215 including switches S0, S1 and S2, a summing device 240, anerror amplifier 230, and a duty cycle controller 220. The regulationcircuit processes an input voltage Vin generated by the voltage source210 to generate and regulate a pair of output voltages Vout1 and Vout2for a pair of loads 290 and 295, respectively.

The voltage source 210, which may be configured as a battery or othertype of voltage source, generates the input voltage Vin at its positiveterminal, and includes a negative terminal coupled to ground. Theinductor L is coupled between the positive terminal of the voltagesource 210 and respective first terminals of switches S1 and S2. Theswitches S1 and S2 include second terminals coupled to first and secondoutputs of the power converter 200 (the nodes at which the first andsecond output voltages Vout and Vout2 are generated, respectively). Thefirst load 290 is coupled between the first output of the powerconverter 200 and ground. The second load 295 is coupled between thesecond output of the power converter 200 and ground. The switch S0 iscoupled between the respective first terminals of the switches S1 and S2and ground.

The summing device 240 sums the first and second output voltages Vout1and Vout2 to generate a common-mode output voltage Vout_cm. The erroramplifier 230 includes a first input configured to receive thecommon-mode output voltage Vout_cm, and a second input configured toreceive a common-mode reference voltage Vref_cm. The common modereference voltage Vref_cm may be related or equal to the sum of a firstreference voltage Vref1 and a second reference voltage Vref2. The firstreference voltage Vref1 is the target voltage for the first outputvoltage Vout1. The second reference voltage Vref2 is the target voltagefor the second output voltage Vout2.

The error amplifier 230 generates a common-mode error voltage Verr_cmrelated to a difference between the common-mode output voltage Vout_cmand the common-mode reference voltage Vref_cm.

The duty cycle controller 220, which receives a substantially periodicclock CLK, generates a control signal duty_simo for controlling the dutycycle ΔT_(S0)/T_(CLK) associated with the switches S0 and S1 turned onand off and switches S0 and S2 turned on and off in two consecutiveperiods of the clock CLK based on the common-mode error voltage Verr_cm,respectively.

FIG. 2B illustrates a timing diagram of exemplary states of switches S0,S1, and S2 and inductor current I_(L) associated with an operation ofthe prior art power converter 200. At time t0 or the beginning of thefirst clock period T_(CLK), the duty cycle controller 220 generates thecontrol signal duty_simo to turn on the switch S0 and turn off switchesS1 and S2. While the switches S0 and S1-S2 are respectfully turned onand off, a current I_(L) flowing through the inductor L increases with aslope related to Vin/L, where L is the inductance of the inductor L. Therising inductor current I_(L) causes the inductor L to store energy inthe form of magnetic flux.

At time t1, the duty cycle controller 220 generates the control signalduty_simo to turn off the switch S0 and turn on switch S, whilemaintaining switch S2 turned off. The duration of the time intervalt0-t1 or duty cycle ΔT_(S0)/T_(CLK) is related to the common-mode errorvoltage Verr_cm. During time interval t1-t2 or the remaining timeinterval of the first clock period T_(CLK), the duty cycle controller220 generates the control signal duty_simo to maintain switches S0 andS2 turned off and switch S1 turned on. The stored magnetic flux createdin the inductor L during time interval t0-t1 produces an inductorcurrent I_(L) that decreases with a slope related to (Vout1−Vin)/L. Asswitch S1 is turned on, the current I_(L) flows to the first output soas to change the first output voltage Vout1 by an amount related to thecommon-mode error voltage Verr_cm.

At time t2 or the start of the second clock period T_(CLK), the dutycycle controller 220 generates the control signal duty_simo to turn onthe switch S0 and turn off switches S1 and S2. While the switches S0 andS1-S2 are respectfully turned on and off, a current I_(L) flowingthrough the inductor L increases with a slope related to Vin/L, where Lis the inductance of the inductor L. The rising inductor current I_(L)causes the inductor L to store energy in the form of magnetic flux.

At time t3, the duty cycle controller 220 generates the control signalduty_simo to turn off the switch S0 and turn on switch S2, whilemaintaining switch S turned off. The duration of the time interval t2-t3or duty cycle ΔT_(S0)/T_(CLK) is related to the common-mode errorvoltage Verr_cm. During time interval t3-t4 or the remaining timeinterval of the second clock period T_(CLK), the duty cycle controller220 generates the control signal duty_simo to maintain switches S0 andS1 turned off and switch S2 turned on. The stored magnetic flux createdin the inductor L during time interval t2-t3 produces an inductorcurrent I_(L) that decreases with a slope related to (Vout2−Vin)/L. Asswitch S2 is turned on, the current I_(L) flows to the second output soas to change the second output voltage Vout2 by an amount related to thecommon-mode error voltage Verr_cm.

Because, during time intervals t0-t1 and t2-t3, the amount of magneticflux stored in the inductor L is related to the common-mode errorvoltage Verr_cm, the releasing of the magnetic flux as an inductorcurrent I_(L) for the first and second loads 290 and 295 during timeintervals t1-t2 and t3-t4, respectively, causes a change in the firstand second output voltages Vout1 and Vout2 based on the common-modeerror voltage Verr_cm. Since the regulation of the output voltages Vout1and Vout2 is based on the common-error voltage Verr_cm, and not theirrespective single-ended error voltages (Vout1−Vref1) and (Vout2−Vref2),the regulation of the output voltages Vout1 and Vout2 does notnecessarily cause the voltages Vout1 and Vout2 to be regulated to Vref1and Vref2, respectively. Rather, the regulation of the first outputvoltage Vout1 is to Vref1−ΔV and the regulation of the second outputvoltage Vout2 is to Vref2+ΔV, or vice-versa; the error ΔV beingsignificant especially when load currents are highly unbalanced. This isreferred to as “cross regulation,” and results in errors in the outputvoltages Vout1 and Vout2.

FIG. 3A illustrates a schematic diagram of another exemplary prior artcurrent control, single-inductor-multiple-output (SIMO) power converter300. The power converter 300 includes a voltage source 310 and aregulation circuit including an inductor L, a switching network 315including switches S0, S1, S2, and S3, a first error amplifier 330, asecond error amplifier 335, and a duty cycle controller 320. Theregulation circuit processes an input voltage Vin generated by thevoltage source 310 to generate and regulate a pair of output voltagesVout1 and Vout2 for a pair of loads 390 and 395, respectively.

The voltage source 310, which may be configured as a battery or othertype of voltage source, generates the input voltage Vin at its positiveterminal, and includes a negative terminal coupled to ground. Theinductor L is coupled between the positive terminal of the voltagesource 310 and respective first terminals of switches S1 and S2. Theswitches S1 and S2 include second terminals coupled to first and secondoutputs of the power converter 300 (the nodes at which the first andsecond output voltages Vout and Vout2 are generated, respectively). Thefirst load 390 is coupled between the first output of the powerconverter 300 and ground. The second load 395 is coupled between thesecond output of the power converter 300 and ground. The switch S0 iscoupled between the respective first terminals of the switches S1 and S2and ground. The switch S3 is coupled across the inductor L.

The first error amplifier 330 includes a first input configured toreceive the first output voltage Vout1, and a second input configured toreceive a first reference voltage Vref1. The first reference voltageVref1 is the target voltage for the first output voltage Vout1. Thefirst error amplifier 330 generates a first error voltage Verr1 relatedto a difference between the first output voltage Vout1 and the firstreference voltage Vref1.

The second error amplifier 335 includes a first input configured toreceive the second output voltage Vout2, and a second input configuredto receive a second reference voltage Vref2. The second referencevoltage Vref2 is the target voltage for the second output voltage Vout2.The second error amplifier 335 generates a second error voltage Verr2related to a difference between the second output voltage Vout2 and thesecond reference voltage Vref2.

The duty cycle controller 320, which receives a substantially periodicclock CLK, generates a control signal duty_simo for controlling the dutycycle ΔT_(S0)/T_(CLK) associated with the switches S0 and S1 turned onand off and switches S0 and S2 turned on and off in two consecutiveperiods of the clock based on the first and second error voltages Verr1and Verr2, respectively. As discussed below, each clock period includesa freewheeling interval.

FIG. 3B illustrates a timing diagram of exemplary states of switches S0,S1, S2, and S3 and inductor current I_(L) associated with an operationof the prior art power converter 300. At time t0 or the start of thefirst clock period T_(CLK), the duty cycle controller 320 generates thecontrol signal duty_simo to turn on the switch S0 and turn off switchesS1, S2 and S3. While the switches S0 and S1-S3 are respectfully turnedon and off during time interval t0-t1, a current I_(L) flowing throughthe inductor L increases with a slope related to Vin/L, where L is theinductance of the inductor L. The rising inductor current I_(L) causesthe inductor L to store energy in the form of magnetic flux.

At time t1, the duty cycle controller 320 generates the control signalduty_simo to turn off the switch S0 and turn on switch S1, whilemaintaining switches S2 and S3 turned off. The duration of the timeinterval t0-t1 or duty cycle ΔT_(S0)/T_(CLK) is related to the firsterror voltage Verr1. During time interval t1-t2, the duty cyclecontroller 320 generates the control signal duty_simo to maintainswitches S0, S2, and S3 turned off and switch S turned on. The storedmagnetic flux created in the inductor L during time interval t0-t1produces an inductor current I_(L) that decreases with a slope relatedto (Vout1−Vin)/L. As switch S1 is turned on, the current I_(L) flows tothe first output so as to change the first output voltage Vout1 by anamount related to the first error voltage Verr1.

At time t2, the duty cycle controller 320 generates the control signalduty_simo to turn on the switch S3, turn off switch S1, and maintainswitches S0 and S2 turned off. While the switches S3 and S0-S2 arerespectfully turned on and off during time interval t2-t3 or theremaining time interval of the first clock period T_(CLK), the switch S3shorts out the inductor L. This interval t2-t3 is referred to as the“freewheeling” interval.

At time t3 or the start of the second clock period T_(CLK), the dutycycle controller 320 generates the control signal duty_simo to turn onthe switch S0 and turn off switches S1, S2 and S3. While the switches S0and S1-S3 are respectfully turned on and off during time interval t3-t4,a current I_(L) flowing through the inductor L increases with a sloperelated to Vin/L, where L is the inductance of the inductor L. Therising inductor current I_(L) causes the inductor L to store energy inthe form of magnetic flux.

At time t4, the duty cycle controller 320 generates the control signalduty_simo to turn off the switch S0 and turn on switch S2, whilemaintaining switches S1 and S3 turned off. The duration of the timeinterval t3-t4 or ΔT_(S0)/T_(CLK) is related to the second error voltageVerr2. During time interval t4-t5, the duty cycle controller 320generates the control signal duty_simo to maintain switches S0, S1, andS3 turned off and switch S2 turned on. The stored magnetic flux createdin the inductor L during time interval t3-t4 produces an inductorcurrent I_(L) that decreases with a slope related to (Vout2−Vin)/L. Asswitch S2 is turned on, the current I_(L) flows to the second output soas to change the second output voltage Vout2 by an amount related to thesecond error voltage Verr2.

At time t5, the duty cycle controller 320 generates the control signalduty_simo to turn on the switch S3, turn off switch S1, and maintainswitches S0 and S2 turned off. While the switches S3 and S0-S2 arerespectfully turned on and off during time interval t5-t6 or theremaining time interval of the second clock period T_(CLK), the switchS3 shorts out the inductor L. This interval is another “freewheeling”interval.

In comparison with power converter 200, the power converter 300regulates the first and second output voltages Vout1 and Vout2 to thereferences voltages Vref1 and Vref2 with more accuracy, respectfully.This is because the “freewheeling” period effectively isolates theregulation interval (t0-t3) of the first output voltage Vout1 from theregulation interval (t3-t6) of the second output voltage Vout2; therebyeffectively eliminating cross regulation. However, the power conversionefficiency in power converter 300 is reduced due to the power consumedduring the “freewheeling” period via the current flowing through theswitch S3 without contributing to the generation of the first and secondoutput voltages Vout1 and Vout2.

FIG. 4A illustrates a schematic diagram of another exemplary switchedcommon-mode current control, single-inductor-multiple-output (SIMO)power converter 400 in accordance with another aspect of the disclosure.

In summary, the power converter 400 regulates first and second outputvoltages as follows:

If the first and second output voltages Vout1 and Vout2 are both lessthan the first and second reference voltages Vref1 and Vref2,respectively, the regulation of the output voltages Vout1 and Vout2 isbased on a common-mode error voltage and performed over two consecutiveclock periods, respectively. Thus, the regulation interval for this casemay be two clock periods in duration.

If the first output voltage Vout1 is greater than the first referencevoltage Vref1, and the second output voltage Vout2 is less than thesecond reference voltage Vref2, the regulation of the first outputvoltage Vout is skipped and the regulation of the second output voltageVout2 is based on the second error voltage Verr2 and performed over asingle clock period. Thus, the regulation interval for this case may bea single period cycle in duration.

If the first output voltage Vout1 is less than the first referencevoltage Vref1, and the second output voltage Vout2 is greater than thesecond reference voltage Vref2, the regulation of the second outputvoltage Vout2 is skipped and the regulation of the first output Vout1 isbased on the first error voltage Verr1 and performed over a single clockcycle. Thus, the regulation interval for this case may be a single clockperiod in duration.

If the first and second output voltages Vout1 and Vout2 are both greaterthe first and second reference voltages Vref1 and Vref2, respectively,the regulation of the output voltage (Vout1 or Vout2) associated with alower load current is skipped, and the regulation of the output voltage(Vout2 or Vout1) is based on the error voltage (Verr2 or Verr1)associated with the load drawing a higher current and performed over asingle clock period. Thus, the regulation interval for this case may bea single clock cycle in duration.

In particular, the power converter 400 includes a voltage source 410 anda regulation circuit including an inductor L, a switching network 415including switches S0, S1, and S2, a first current-sense resistorR_(S1), and a second current-sense resistor R_(S2). The regulationcircuit further includes a first error amplifier 430, a second erroramplifier 450, a first comparator 435, a second comparator 445, and athird comparator 440. Additionally, the regulation circuit includes alogic circuit 460, a fourth switch S4, a fifth switch S5, a summingdevice 465, and a duty cycle controller 420. The regulation circuitprocesses an input voltage Vin generated by the voltage source 410 togenerate and regulate a pair of output voltages Vout1 and Vout2 for apair of loads 490 and 495, respectively.

The voltage source 410, which may be configured as a battery or othertype of voltage source, generates the input voltage Vin at its positiveterminal, and includes a negative terminal coupled to ground. Theinductor L is coupled between the positive terminal of the voltagesource 410 and respective first terminals of switches S1 and S2. Thefirst and second current-sensing resistors R_(S1) and R_(S2) are coupledbetween respective second terminals of the switches S1 and S2 and thefirst and second outputs of the power converter 400 (the nodes at whichthe first and second output voltages Vout1 and Vout2 are generated,respectively). The first load 490 is coupled between the first output ofthe power converter 400 and ground. The second load 495 is coupledbetween the second output of the power converter 400 and ground. Theswitch S0 is coupled between the respective first terminals of theswitches S1 and S2 and ground.

The first error amplifier 430 includes a first input configured toreceive the first output voltage Vout1, and a second input configured toreceive a first reference voltage Vref1. The first reference voltageVref1 is the target voltage for the first output voltage Vout1. Thefirst error amplifier 430 generates a first error voltage Verr1 relatedto a difference between the first output voltage Vout1 and the firstreference voltage Vref1.

Similarly, the second error amplifier 450 includes a first inputconfigured to receive the second output voltage Vout2, and a secondinput configured to receive a second reference voltage Vref2. The secondreference voltage Vref2 is the target voltage for the second outputvoltage Vout2. The second error amplifier 450 generates a second errorvoltage Verr2 related to a difference between the second output voltageVout2 and the second reference voltage Vref2.

The first comparator 435 includes a first (e.g., positive) inputconfigured to receive the first output voltage Vout1, and a second(e.g., negative) input configured to receive the first reference voltageVref1. The first comparator 435 generates a signal VOK1 indicatingwhether the first output voltage Vout1 is greater than the firstreference voltage Vref1. In this example, if the first output voltageVout1 is greater than the first reference voltage Vref1, the firstcomparator 435 generates the signal VOK1 at a high logic level (e.g., alogic one (1)). If the first output voltage Vout1 is less than the firstreference voltage Vref1, the first comparator 435 generates the signalVOK1 at a low logic level (e.g., a logic zero (0)).

Similarly, the second comparator 445 includes a first (e.g., positive)input configured to receive the second output voltage Vout2, and asecond (e.g., negative) input configured to receive the second referencevoltage Vref2. The second comparator 445 generates a signal VOK2indicating whether the second output voltage Vout2 is greater than thesecond reference voltage Vref2. In this example, if the second outputvoltage Vout2 is greater than the second reference voltage Vref2, thesecond comparator 445 generates the signal VOK2 at a high logic level(e.g., a logic one (1)). If the second output voltage Vout2 is less thanthe second reference voltage Vref2, the second comparator 445 generatesthe signal VOK2 at a low logic level (e.g., a logic zero (0)).

The third comparator 440 includes a first (e.g., positive) inputconfigured to receive a voltage ΔV₁ across the first current-senseresistor R_(S1), and a second (e.g., negative) input configured to avoltage ΔV₂ across the second current-sense resistor R_(S2). The voltageΔV₁ is related to the current being supplied to the first load 490, andthe voltage ΔV₂ is related to the current being supplied to the secondload 495. The third comparator 440 generates a signal VLM indicatingwhether the voltage ΔV₁ is greater than the voltage ΔV₂. In other words,the signal VLM indicates which of the loads 490 or 495 is drawing morecurrent. In this example, if the voltage ΔV₁ is greater than the voltageΔV₂, the third comparator 440 generates the signal VLM at a high logiclevel (e.g., a logic one (1)). If the voltage ΔV₁ is less than thevoltage ΔV₂, the third comparator 440 generates the signal VLM at a lowlogic level (e.g., a logic zero (0)).

The logic circuit 460 synchronously controls the ON/OFF states of thefourth and fifth switches S4-S5 and the first and second switches S1 andS2 via the S1/S2_SEL signal based on the signals VOK1, VOK2, and VLM anda clock CLK, as discussed in more detail below. The summing device 465generates an effective error voltage Verr_eff based on the first errorvoltage Verr1, the second error voltage Verr2, or the sum of the firstand second error voltages Verr1 and Verr2, based on the states of thesignals VOK1, VOK2, and VLM.

The duty cycle controller 420, which receives the substantially periodicclock CLK and the S1/S2_SEL signal, generates a control signal duty_simofor controlling the duty cycle ΔT_(S0)/T_(CLK) associated with theswitches S0 and S1 or S2 turned on and off in a first clock cycle basedon the effective error voltage Verr_eff, and the switches S0 and S2 if asecond clock cycle is required based on the effective error voltageVerr_eff, respectively.

FIG. 4B illustrates a table for explaining an operation of the logiccircuit 460 in accordance with another aspect of the disclosure.

According to the table, if the signals VOK1 and VOK2 are both at logiczeros (0s) (meaning that the first and second output voltages Vout1 andVout2 are less than the first and second reference voltages Vref1 andVref2, respectively), the logic circuit 460, at the beginning of thefirst clock cycle, turns on switches S4 and S5 regardless of the stateof the VLM signal. In this scenario, the summing device 465 generatesthe effective error voltage Verr_eff as substantially the common-modeerror voltage Verr_cm associated with the first and second outputvoltages Vout1 and Vout2 throughout the first and second clock cycles.At the beginning of the first clock cycle, the logic circuit 560configures the S1/S2_SEL signal to select S1 for regulation of the firstoutput voltage Vout1 during the first clock cycle, then configures theS1/S2_SEL signal to select S2 for regulation of the second outputvoltage Vout2 during the second clock cycle.

If the signal VOK1 is at a logic one (1) and the signal VOK2 is at alogic zero (0) (meaning that the first output voltage Vout1 is greaterthan the first reference voltage Vref1 and the second output voltageVout2 is less than the second reference voltage Vref2), the logiccircuit 460, at the beginning of the single-clock-cycle regulationinterval, turns off switch S4 and turns on switch S5 regardless of thestate of the VLM signal. In this scenario, the summing device 465generates the effective error voltage Verr_eff as substantially thesecond error voltage Verr2. Also, at the beginning of the single clockcycle, the logic circuit 560 configures the S1/S2_SEL signal to selectS2 for regulation of the second output voltage Vout2 during the singleclock cycle. As discussed, the regulation of the first output voltageVout1 is skipped during this regulation interval.

Similarly, if the signal VOK1 is at a logic zero (0) and the signal VOK2is at a logic one (1) (meaning that the first output voltage Vout1 isless than the first reference voltage Vref1 and the second outputvoltage Vout2 is greater than the second reference voltage Vref2), thelogic circuit 460, at the beginning of the single-clock-cycle regulationinterval, turns on switch S4 and turns off switch S5 regardless of thestate of the VLM signal. In this scenario, the summing device 465generates the effective error voltage Verr_eff as substantially thefirst error voltage Verr1. Also, at the beginning of the single clockcycle, the logic circuit 560 configures the S1/S2_SEL signal to selectS1 for regulation of the first output voltage Vout1 during the singleclock cycle. As discussed, the regulation of the second output voltageVout2 is skipped during this regulation interval.

If the signals VOK1 and VOK2 are both at logic ones (1s) (meaning thatthe first and second output voltages Vout1 and Vout2 are greater thanthe first and second reference voltages Vref1 and Vref2, respectively),the logic circuit 460, at the beginning of the single-clock-cycleregulation interval, turns on S4 or S5 based on the state of the VLMsignal.

For instance, if the VLM signal is at a logic one (1) (meaning that thefirst load 490 is drawing more current than the second load 495), thelogic circuit 460 turns on switch S4 and turns off switch S5. In thisscenario, the summing device 465 generates the effective error voltageVerr_eff as substantially the first error voltage Verr1. If the VLMsignal is at a logic zero (0) (meaning that the second load 495 isdrawing more current than the first load 490), the logic circuit 460turns off switch S4 and turns off switch S5. In this scenario, thesumming device 465 generates the effective error voltage Verr_eff assubstantially the second error voltage Verr2.

Also, at the beginning of the single clock cycle, the logic circuit 560configures the S1/S2_SEL signal to select S1 or S2 for regulation of thefirst or second output voltage Vout1 or Vout2 during the single clockcycle. As discussed, the regulation of the output voltage associatedwith the smaller load current is skipped during this regulationinterval.

Thus, if the signals VOK1 and VOK2 are both logic zeros (0s), theoperation of the power converter 400 is in accordance with regulatingboth output voltages Vout and Vout2 over two consecutive clock cyclesbased on the common-mode error voltage Verr_cm as depicted in FIG. 2B.

If the signal VOK1 is at a logic one (1) and VOK2 is at a logic zero(0), the operation of the power converter 400 is in accordance withregulating only the second output voltage Vout2 over a single clockcycle based on the second error voltage Verr2 as depicted in FIG. 1B,and skipping the regulation of the first output voltage Vout1 for thisregulation interval.

If the signal VOK1 is at a logic zero (0) and VOK2 is at a logic one(1), the operation of the power converter 400 is in accordance withregulating only the first output voltage Vout1 over a single clock cyclebased on the first error voltage Verr1 as depicted in FIG. 1B, andskipping the regulation of the second output voltage Vout2 for thisregulation interval.

If the signals VOK1 and VOK2 are both logic ones (1s), the operation ofthe power converter 400 is in accordance with regulating only the outputvoltage Vout1 or Vout2 over a single clock cycle as depicted in FIG. 1B,based on the error voltage Verr1 or Verr2 associated with the load 490or 495 drawing the greater amount of current as indicated by voltagesΔV₁ and ΔV₂ across the current-sense resistor R_(S1) and R_(S2),respectively.

In comparison with power converter 300, the power converter 400 does notinclude a freewheeling interval. Thus, power converter 400 does notsuffer from power efficiency reduction due to freewheeling intervals.The regulation inaccuracy by always using a common-mode error voltage asin power converter 200 is only present in power converter 400 when thefirst and second output voltages Vout1 and Vout2 are less than the firstand second reference voltages Vref1 and Vref2, respectively. Otherwise,the error voltage associated with the output voltage to be regulatedduring the current regulation interval is used for more accuracy. Thus,overall, the power converter 400 provides a more accurate regulation ofthe first and second output voltages Vout and Vout2 compared to that ofpower converter 200.

FIG. 5 illustrates a schematic diagram of an exemplary regulationcircuit 500 for controlling the duty cycle associated with switches S0and S1 or S2 of the power converter 400 in accordance with anotheraspect of the disclosure. The regulation circuit 500 is an exemplarymore detailed implementation of a portion of the regulation circuit inpower converter 400.

The regulation circuit 500 includes a first differentialtransconductance amplifier 510, a second differential transconductanceamplifier 520, switches S4 and S5, current summer 530, compensationnetwork 540, a current source 545, a resistor R, a pulse width modulator550, an RS-flip-flop 560, an inverter 570, a demultiplexer 580, and alogic circuit 590.

The first differential transconductance amplifier 510 includes apositive input configured to receive the first output voltage Vout1, anegative input configured to receive the first reference voltage Vref1,and an output configured to generate a first error current Ierr1 relatedto a difference between the first output voltage Vout1 and the firstreference voltage Vref1. The first differential transconductanceamplifier 510 performs a similar operation as the first error amplifier430 of power converter 400.

The second differential transconductance amplifier 520 includes apositive input configured to receive the second output voltage Vout2, anegative input configured to receive the second reference voltage Vref2,and an output configured to generate a second error current Ierr2related to a difference between the second output voltage Vout2 and thesecond reference voltage Vref2. The second differential transconductanceamplifier 520 performs a similar operation as the second error amplifier450 of power converter 400.

The switches S4 and S5 are coupled between the outputs of the first andsecond differential transconductance amplifiers 510 and 520 and firstand second inputs of the current summer 530. The ON/OFF states of theswitches S4 and S5 are controlled by the logic circuit 590 in accordancewith signals VOK1, VOK2, and VLM, as previously discussed with referenceto logic circuit 460 of power converter 400. The current summer 530 sumsthe currents flowing into the first and second inputs of the currentsummer to generate an effective error current Ierr_eff. The currentsummer 530 performs a similar operation as the summing device 465 ofpower converter 400.

The compensation network 540 includes a parasitic capacitor C_(P)coupled in parallel with a resistor R_(Z) connected in series with acapacitor C_(Z) between the output of the current summer 530 and ground.The effective error current Ierr_eff flows into the compensation network540 to generate an effective error voltage Verr_eff. This effectiveerror voltage Verr_eff corresponds to the effective error voltageVerr_eff described with reference to power converter 400.

The current source 545 and resistor R is coupled between an uppervoltage rail VDD and ground. The current source 545 is configured togenerate a replica current I_(LR) related to the inductor current I_(L)(e.g., a scaled version thereof generated via a current mirror). Thereplica current I_(LR) flows through the resistor R to generate avoltage V_(LR) related to the inductor current I_(L). The voltagesV_(LR) and Verr_eff are applied to positive and negative inputs of thepulse width modulator 550.

The output of the pulse width modulator 550 is coupled to a reset (R)input of the RS-flip-flip 560. The clock CLK is applied to the set (S)input of the RS-flip-flop 560. The output of the RS-flip-flop 560controls the ON/OFF state of the switch S0. The output of theRS-flip-flop 560 is coupled to an input of the inverter 570. The outputof the inverter 570 is coupled to an input of the demultiplexer 580. Thecurrent source 545, resistor R, compensation network 540, pulse widthmodulator 550, RS-flip-flop 560, inverter 570, and demultiplexer 580 maybe integrated in the duty cycle controller 420 of power converter 400.

The logic circuit 590 receives the signals VOK1, VOK2, and VLM andcontrols the switches S4 and S5 and the selection (S1/S2_SEL) performedby the demultiplexer 580 based on the clock CLK, as previously describedwith reference to power converter 400.

The operation of regulation circuit 500 is as follows: if VOK1 and VOK2are both logic zeros (0s) at the beginning of a first regulation clockcycle, the logic circuit 590 turns on switches S4 and S5. Accordingly,the effective error voltage Verr_eff is based on the common-mode errorvoltage Verr_cm associated with the first and second output voltagesVout1 and Vout2. The effective error voltage Verr_eff is the thresholdvoltage for the pulse width modulator 550.

Further, at the beginning of the first regulation clock cycle, marked bythe rising edge of the clock CLK, the RS-flip-flop 560 generates a highlogic signal to turn on the switch S0 and cause the inductor currentI_(L) to rise with a slope of Vin/L. At such time, the logic circuit 590has configured the demultiplexer 580 to select switch S1. Thus, theinverter 570 inverts the high logic signal from the RS-flip-flip 560 togenerate a low logic signal. The demultiplexer 580 passes the low logicsignal to turn off or maintain switch S1 off. The voltage V_(LR) risesin accordance with the inductor current I_(L).

When the voltage V_(LR) reaches the effective error voltage Verr_eff,the pulse width modulator 550 transitions its output from a low logicsignal to a high logic signal. The high logic signal resets theRS-flip-flop 560 causing it to output a low logic signal. The low logicsignal turns off switch S0. The inverter 570 inverts the low logicsignal to generate a high logic signal. The demultiplexer 580 passes thehigh logic signal to turn on switch S1. Thus, the magnetic energy storedin the inductor L due to the rising inductor current I_(L) while switchS0 was on flows into the first load to change the first output voltageVout1 by an amount related to the effective error voltage Verr_eff.

Since, when VOK1 and VOK2 are both logic zeros (0s), the regulationinterval is two clock cycles. During the second regulation clock cycle,the effective error voltage Verr_eff remains the same as in the firstregulation clock cycle. Accordingly, at the beginning of the secondregulation clock cycle, marked by the rising edge of the clock CLK, theRS-flip-flop 560 generates a high logic signal to turn on the switch S0and cause the inductor current I_(L) to rise with a slope of Vin/L. Atsuch time, the logic circuit 590 has now configured the demultiplexer580 to select switch S2. Thus, the inverter 570 inverts the high logicsignal from the RS-flip-flip 560 to generate a low logic signal. Thedemultiplexer 580 passes the low logic signal to turn off or maintainswitch S2 off. The voltage V_(LR) rises in accordance with the inductorcurrent I_(L).

When the voltage V_(LR) reaches the effective error voltage Verr_eff,the pulse width modulator 550 transitions its output from a low logicsignal to a high logic signal. The high logic signal resets theRS-flip-flop 560 causing it to output a low logic signal. The low logicsignal turns off switch S0. The inverter 570 inverts the low logicsignal to generate a high logic signal. The demultiplexer 580 passes thehigh logic signal to turn on switch S2. Thus, the magnetic energy storedin the inductor L due to the rising inductor current I_(L) while switchS0 was on flows into the second load to change the second output voltageVout2 by an amount related to the effective error voltage Verr_eff.

If VOK1 is at a logic one (1) and VOK2 is at a logic zero (0) at thebeginning of a regulation interval, the logic circuit 590 turns offswitch S4 and turns on switch S5. Accordingly, the effective errorvoltage Verr_eff is based on the second error voltage Verr2 associatedwith the second output voltage Vout2. The effective error voltageVerr_eff is the threshold voltage for the pulse width modulator 550.

Further, at the beginning of the regulation interval, marked by therising edge of the clock CLK, the RS-flip-flop 560 generates a highlogic signal to turn on the switch S0 and cause the inductor currentI_(L) to rise with a slope of Vin/L. At such time, the logic circuit 590has configured the demultiplexer 580 to select switch S2. Thus, theinverter 570 inverts the high logic signal from the RS-flip-flip 560 togenerate a low logic signal. The demultiplexer 580 passes the low logicsignal to turn off or maintain switch S2 off. The voltage V_(LR) risesin accordance with the inductor current I_(L).

When the voltage V_(LR) reaches the effective error voltage Verr_eff,the pulse width modulator 550 transitions its output from a low logicsignal to a high logic signal. The high logic signal resets theRS-flip-flop 560 causing it to output a low logic signal. The low logicsignal turns off switch S0. The inverter 570 inverts the low logicsignal to generate a high logic signal. The demultiplexer 580 passes thehigh logic signal to turn on switch S2. Thus, the magnetic energy storedin the inductor L due to the rising inductor current I_(L) while switchS0 was on flows into the second load to change the second output voltageVout2 by an amount related to the effective error voltage Verr_eff. Inthis case, the regulation interval is only a single clock cycle.

If VOK1 is at a logic zero (0) and VOK2 is at a logic one (1) at thebeginning of a regulation interval, the logic circuit 590 turns onswitch S4 and turns off switch S5. Accordingly, the effective errorvoltage Verr_eff is based on the first error voltage Verr1 associatedwith the first output voltage Vout1. The effective error voltageVerr_eff is the threshold voltage for the pulse width modulator 550.

Further, at the beginning of the regulation interval, marked by therising edge of the clock CLK, the RS-flip-flop 560 generates a highlogic signal to turn on the switch S0 and cause the inductor currentI_(L) to rise with a slope of Vin/L. At such time, the logic circuit 590has configured the demultiplexer 580 to select switch S1. Thus, theinverter 570 inverts the high logic signal from the RS-flip-flip 560 togenerate a low logic signal. The demultiplexer 580 passes the low logicsignal to turn off or maintain switch S1 off. The voltage V_(LR) risesin accordance with the inductor current I_(L).

When the voltage V_(LR) reaches the effective error voltage Verr_eff,the pulse width modulator 550 transitions its output from a low logicsignal to a high logic signal. The high logic signal resets theRS-flip-flop 560 causing it to output a low logic signal. The low logicsignal turns off switch S0. The inverter 570 inverts the low logicsignal to generate a high logic signal. The demultiplexer 580 passes thehigh logic signal to turn on switch S1. Thus, the magnetic energy storedin the inductor L due to the rising inductor current I_(L) while switchS0 was on flows into the first load to change the first output voltageVout1 by an amount related to the effective error voltage Verr_eff. Inthis case, the regulation interval is only a single clock cycle.

If both VOK1 and VOK2 are both at a logic ones (1s) at the beginning ofa regulation interval, and the first load is drawing more current thanthe second load, the logic circuit 590 turns on switch S4 and turns offswitch S5. Accordingly, the effective error voltage Verr_eff is based onthe first error voltage Verr1 associated with the first output voltageVout1. The effective error voltage Verr_eff is the threshold voltage forthe pulse width modulator 550.

Further, at the beginning of the regulation interval, marked by therising edge of the clock CLK, the RS-flip-flop 560 generates a highlogic signal to turn on the switch S0 and cause the inductor currentI_(L) to rise with a slope of Vin/L. At such time, the logic circuit 590has configured the demultiplexer 580 to select switch S1. Thus, theinverter 570 inverts the high logic signal from the RS-flip-flip 560 togenerate a low logic signal. The demultiplexer 580 passes the low logicsignal to turn off or maintain switch S1 off. The voltage V_(LR) risesin accordance with the inductor current I_(L).

When the voltage V_(LR) reaches the effective error voltage Verr_eff,the pulse width modulator 550 transitions its output from a low logicsignal to a high logic signal. The high logic signal resets theRS-flip-flop 560 causing it to output a low logic signal. The low logicsignal turns off switch S0. The inverter 570 inverts the low logicsignal to generate a high logic signal. The demultiplexer 580 passes thehigh logic signal to turn on switch S1. Thus, the magnetic energy storedin the inductor L due to the rising inductor current I_(L) while switchS0 was on flows into the first load to change the first output voltageVout1 by an amount related to the effective error voltage Verr_eff. Inthis case, the regulation interval is only a single clock cycle.

If both VOK1 and VOK2 are both at a logic ones (1s) at the beginning ofa regulation interval, and the second load is drawing more current thanthe first load, the logic circuit 590 turns on switch S5 and turns offswitch S4. Accordingly, the effective error voltage Verr_eff is based onthe second error voltage Verr2 associated with the second output voltageVout2. The effective error voltage Verr_eff is the threshold voltage forthe pulse width modulator 550.

Further, at the beginning of the regulation interval, marked by therising edge of the clock CLK, the RS-flip-flop 560 generates a highlogic signal to turn on the switch S0 and cause the inductor currentI_(L) to rise with a slope of Vin/L. At such time, the logic circuit 590has configured the demultiplexer 580 to select switch S2. Thus, theinverter 570 inverts the high logic signal from the RS-flip-flip 560 togenerate a low logic signal. The demultiplexer 580 passes the low logicsignal to turn off or maintain switch S2 off. The voltage V_(LR) risesin accordance with the inductor current I_(L).

When the voltage V_(LR) reaches the effective error voltage Verr_eff,the pulse width modulator 550 transitions its output from a low logicsignal to a high logic signal. The high logic signal resets theRS-flip-flop 560 causing it to output a low logic signal. The low logicsignal turns off switch S0. The inverter 570 inverts the low logicsignal to generate a high logic signal. The demultiplexer 580 passes thehigh logic signal to turn on switch S2. Thus, the magnetic energy storedin the inductor L due to the rising inductor current I_(L) while switchS0 was on flows into the second load to change the second output voltageVout2 by an amount related to the effective error voltage Verr_eff. Inthis case, the regulation interval is only a single clock cycle.

FIG. 6 illustrates a schematic diagram of another exemplary switchedcommon-mode current control, single-inductor-multiple-output (SIMO)power converter 600 in accordance with another aspect of the disclosure.The regulation technique performed by power converter 400 may beextended to regulating N number of output voltages Vout1 to VoutN usinga single inductor, where N is an integer of two or more.

In particular, the power converter 600 includes a voltage source 610 anda regulation circuit including an inductor L, a switching network 615including a set of switches S0 to SN, and a set of current-senseresistors R_(S1)-R_(SN). The regulation circuit further includes a setof error amplifiers 630-1 to 630-N, a set of comparators 640-1 to 640-N,and a load comparator 650. Additionally, the power converter 600includes a logic circuit 660, a set of switches SW1 to SWN, a summingdevice 665, and a duty cycle controller 620. The regulation circuitprocesses an input voltage Vin generated by the voltage source 610 togenerate and regulate a set of output voltages Vout1 to VoutN for a setof loads 690-1 to 690-N, respectively.

The voltage source 610, which may be configured as a battery or othertype of voltage source, generates the input voltage Vin at its positiveterminal, and includes a negative terminal coupled to ground. Theinductor L is coupled between the positive terminal of the voltagesource 610 and respective first terminals of the set of switches S1 toSN. The set of current-sensing resistors R_(S1) to R_(SN) are coupledbetween respective second terminals of the set of switches S1 to SN anda set of outputs of the power converter 600 (the nodes at which the setof output voltages Vout1 to VoutN are generated, respectively). The setof loads 690-1 to 690-N are coupled between the set of outputs of thepower converter 600 and ground, respectively. The switch S0 is coupledbetween the respective first terminals of the set of switches S1 to SNand ground.

The set of error amplifiers 630-1 to 630-N include respective firstinputs configured to receive the set of output voltages Vout1 to VoutN,and respective second inputs configured to receive a set of referencevoltages Vref1 to VrefN. The set of reference voltages Vref1 to VrefNare the target voltages for the set of output voltages Vout1 to VoutN,respectively. The set of error amplifiers 630-1 to 630-N generate a setof error voltages Verr1 to VerrN related to differences between the setof output voltages Vout1 to VoutN and the set of reference voltagesVref1 to VrefN, respectively.

The set of comparators 640-1 to 640-N include respective first (e.g.,positive) inputs configured to receive the set of output voltages Vout1to VoutN, and respective second (e.g., negative) inputs configured toreceive the set of reference voltages Vref1 to VrefN. The set ofcomparators 640-1 to 640-N generate a set of signals VOK1 to VOKNindicating whether the set of output voltages Vout1 to VoutN are greaterthan the set of reference voltages Vref1 to VrefN, respectively.

The load comparator 650 includes a set of inputs configured to receive aset of voltages ΔV₁ to ΔV_(N) across the set of current-sense resistorR_(S1) to R_(SN), respectively. The load comparator 650 generates asignal VLM indicating which of the set of voltage ΔV₁ to ΔV_(N) isgreatest to indicate which of the set of loads 690-1 to 690-N is drawingthe most current.

The logic circuit 660 synchronously controls the ON/OFF states of theset of switches SW1 to SWN and the set of switches S1 to SN via theS1-SN_SEL signal based on the set of signals VOK1 to VOKN, the signalVLM, and a clock CLK, as discussed in more detail below. The summingdevice 665 generates an effective error voltage Verr_eff based on atleast one or more of the set of error voltages Verr1 to VerrN.

The duty cycle controller 620, which receives the substantially periodicclock CLK and the S1-SN_SEL signal, generates a control signal duty_simofor controlling the duty cycle ΔT_(S0)/T_(CLK) associated with theswitch S0 versus the selected switches S1 to SN for the selected numberof regulation clock cycles based on the effective error voltageVerr_eff.

FIG. 7 illustrates a flow diagram of an exemplary method 700 ofoperating the power converter 600 in accordance with another aspect ofthe disclosure.

According to the method 700, for the current regulation interval, thelogic circuit 660 determines whether one or more of the set of outputvoltages Vout1 to VoutN are less than the set of reference voltagesVref1 to VrefN, respectively (block 710). The logic circuit 660 may makethis determination based on the states of the set of signals VOK1 toVOKN, respectively.

Further, according to the method 700, if the logic circuit 660, in block720, determines that one or more of the set of output voltages Vout toVoutN are less than the corresponding one or more of the set ofreference voltages Vref1 to VrefN, respectively, the logic circuit 660causes the generation of the effective error voltage Verr_eff to bebased on the one or more error voltages associated with the one or moreoutput voltages that are less than the one or more correspondingreference voltages (block 730). The logic circuit 660 may perform thisby turning on one or more of the set of switches SW1 to SWN associatedwith the one or more output voltages that are less than the one or morecorresponding reference voltages; thereby allowing the summing device665 to generate the effective error voltage Verr_eff.

Then, according to the method 700, the one or more output voltages thatare less than the corresponding one or more reference voltages areregulated based on the effective error voltage Verr_eff over a number ofclock cycles (in a time-multiplexed manner) equal to the number of oneor more output voltages that are less than the corresponding one or morereference voltages (block 740). The duty cycle controller 620, based onthe clock CLK and the S1-SN_SEL signal from the logic circuit 660,controls the ON/OFF states of switch S0 and one or more of the set ofswitches S1 to SN corresponding to the one or more output voltages thatneed to be regulated during the current regulation interval.

If, in block 720 of the method 700, the logic circuit 660 determinesthat none of the output voltages Vout1 to VoutN are less than thecorresponding reference voltages Vref1 to VrefN based on the states ofthe VOK1 to VOKN signals, then the logic circuit 660 determines whichload of the set of loads 690-1 to 690-N is drawing the most current(block 750). The logic circuit 660 may make this determination based onthe state of the VLM signal.

Then, according to the method 700, the logic circuit 660 causes thegeneration of the effective error voltage Verr_eff to be basedsubstantially on error voltage associated with the load drawing the mostcurrent (block 760). The logic circuit 660 may perform this by turningon only the switch among the set of switches SW1 to SWN associated withload drawing the most current; thereby allowing the summing device 665to generate the effective error voltage Verr_eff.

Then, according to the method 700, the output voltage associated withthe load drawing the most current is regulated based on the effectiveerror voltage over a single clock cycle (block 770). The duty cyclecontroller 620, based on the clock CLK and the S1-SN_SEL signal from thelogic circuit 660, controls the ON/OFF states of switch S0 and theswitch (one of switches S1 to SN) corresponding to the load drawing themost current to regulate the corresponding output voltage for thecurrent regulation interval.

After completion of the operation specified in block 740 or 770,according to the method 700, the regulation of one or more of the outputvoltages proceeds to the next regulation interval where the operationsstarting with block 710 are performed as discussed above (block 780).

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples described herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed herein.

The invention claimed is:
 1. An apparatus, comprising: a voltage sourceconfigured to generate an input voltage; and a regulation circuitconfigured to generate a set of output voltages based on the inputvoltage, wherein the regulation circuit is configured to change only asubset of or the entire set of output voltages using the input voltagein a current regulation interval based on different scenarios regardingwhether the set of output voltages are greater or less than a set ofcorresponding reference voltages, respectively; wherein the regulationcircuit is configured to change only one of the output voltage over thecurrent regulation interval if the output voltages of the entire set aregreater than the corresponding reference voltages, wherein the one ofthe output voltage is associated with a load drawing the most currentamong one or more loads associated with the remaining one or more outputvoltages of the set.
 2. The apparatus of claim 1, wherein the regulationcircuit is configured to change only one of the output voltage over thecurrent regulation interval if the one of the output voltage is lessthan the corresponding reference voltages, and the remaining one or moreoutput voltages of the set are greater than the one or morecorresponding reference voltages.
 3. The apparatus of claim 2, whereinthe regulation circuit is configured to change the only one of theoutput voltage based on an error voltage related to a difference betweenthe only one of the output voltage and the corresponding referencevoltage.
 4. The apparatus of claim 2, wherein a duration of the currentregulation interval is one or more periods of a clock.
 5. An apparatus,comprising: a voltage source configured to generate an input voltage;and a regulation circuit configured to generate a set of output voltagesbased on the input voltage, wherein the regulation circuit is configuredto change only a subset of or the entire set of output voltages usingthe input voltage in a current regulation interval based on differentscenarios regarding whether the set of output voltages are greater orless than a set of corresponding reference voltages, respectively;wherein the regulation circuit is configured to change only the subsetof the set of output voltages over the current regulation interval ifthe output voltages of the subset are less than the correspondingreference voltages, and the remaining one or more output voltages of theset is greater than the one or more corresponding reference voltages;wherein the regulation circuit is configured to change only the subsetof the output voltages over the current regulation interval in a timemultiplexed manner.
 6. The apparatus of claim 1, wherein the regulationcircuit is configured to change the entire set of output voltages overthe current regulation interval if the entire set of output voltages areless than the corresponding reference voltages.
 7. The apparatus ofclaim 6, wherein the regulation circuit is configured to change theentire set of output voltages based on an error voltage related todifferences between the entire set of output voltages and thecorresponding reference voltages, respectively.
 8. The apparatus ofclaim 7, wherein the error voltage is related to an average of thedifferences between the entire set of output voltages and thecorresponding reference voltages, respectively.
 9. The apparatus ofclaim 6, wherein the regulation circuit is configured to change theentire set of the output voltages over the current regulation intervalin a time multiplexed manner.
 10. The apparatus of claim 9, wherein eachsubinterval for changing each of the output voltage in the entire sethas a duration of one or more periods of a clock.
 11. The apparatus ofclaim 1, wherein the regulation circuit is configured to change the onlyone of the output voltage based on an error voltage related to adifference between the only one of the output voltage and thecorresponding reference voltage.
 12. The apparatus of claim 5, whereineach subinterval for regulating each of the output voltage in the subsethas a duration of one or more periods of a clock.
 13. The apparatus ofclaim 12, wherein the regulation circuit is configured to change onlythe subset of the output voltages based on an error voltage related todifferences between the subset of output voltages and the correspondingreference voltages, respectively.
 14. The apparatus of claim 13, whereinthe error voltage is related to an average of the differences betweenthe subset of output voltages and the corresponding reference voltages,respectively.
 15. A method, comprising: generating an input voltage;generating a set of output voltages based on the input voltage; andchanging only a subset of or the entire set of output voltages using theinput voltage in a current regulation interval based on differentscenarios regarding whether the set of output voltages are greater orless than a set of corresponding reference voltages, respectively;wherein changing only the subset of the set of output voltages compriseschanging only one of the output voltages over the current regulationinterval if the output voltages of the entire set are greater than thecorresponding reference voltages, wherein the only one of the outputvoltage is associated with a load drawing the most current among one ormore loads associated with the remaining one or more output voltages ofthe set.
 16. The method of claim 15, wherein changing only the subset ofthe set of output voltages comprises changing only the subset of the setof output voltages over the current regulation interval if the one ormore output voltages of the subset are less than the corresponding oneor more reference voltages, and the remaining one or more outputvoltages of the set is greater than the one or more correspondingreference voltages.
 17. The method of claim 16, wherein changing onlythe subset of one or more output voltages comprises changing the subsetof one or more output voltages based on an error voltage related to oneor more differences between the one or more output voltages of thesubset and the one or more corresponding reference voltages,respectively.
 18. The method of claim 15, wherein changing the entireset of output voltages comprises changing the entire set of outputvoltages over the current regulation interval if the entire set ofoutput voltages are less than the corresponding reference voltages. 19.The method of claim 18, wherein changing the entire set of outputvoltages is based on an error voltage related to differences between theentire set of output voltages and the corresponding reference voltages,respectively.
 20. The method of claim 15, wherein changing the only oneof the output voltage comprises changing the only one of the outputvoltage based on an error voltage related to a difference between theonly one of the output voltage and the corresponding reference voltage.21. An apparatus, comprising: means for generating an input voltage;means for generating a set of output voltages based on the inputvoltage; and means for changing only a subset of or the entire set ofoutput voltages using the input voltage in a current regulation intervalbased on different scenarios regarding whether the set of outputvoltages are greater or less than a set of corresponding referencevoltages, respectively; wherein the means for changing only the subsetof the set of output voltage comprises means for changing only one ofthe output voltages over the current regulation interval if the outputvoltages of the entire set are greater than the corresponding referencevoltages, wherein the only one of the output voltage is associated witha load drawing the most current among one or more loads associated withthe remaining one or more output voltages of the set.
 22. The apparatusof claim 21, wherein the means for changing only the subset of the setof output voltages comprises means for changing only the subset of theset of output voltages over the current regulation interval if the oneor more output voltages of the subset are less than the correspondingone or more reference voltages, and the remaining one or more outputvoltages of the set is greater than the one or more correspondingreference voltages.
 23. The apparatus of claim 22, wherein the means forchanging only the subset of one or more output voltages comprises meansfor regulating the subset of one or more output voltages based on anerror voltage related to one or more differences between the one or moreoutput voltages of the subset and the one or more correspondingreference voltages, respectively.
 24. The apparatus of claim 21, whereinthe means for changing the set of output voltages comprises means forchanging the entire set of output voltages over the current regulationinterval if the entire set of output voltages are less than thecorresponding reference voltages.
 25. The apparatus of claim 24, whereinthe means for changing the entire set of output voltages comprises meansfor changing the entire set of output voltages based on an error voltagerelated to differences between the entire set of output voltages and thecorresponding reference voltages, respectively.
 26. The apparatus ofclaim 21, wherein the means for changing the only one of the outputvoltage comprises means for changing the only one of the output voltagebased on an error voltage related to a difference between the only oneof the output voltage and the corresponding reference voltage.